The present invention relates to a chemical warmer, and especially to a chemically heated blanket.
A chemical warmer has many known advantages and uses since no flame is produced. It is widely used in hospitals, homes and outdoors for applying heat to a human body or other objects. Consequently, various types of such devices are known in the art. Many improvements have been made in the chemical exothermic materials used in the chemical warmers, one useful type uses air for activating and maintaining the thermogenic chemical reactions in the chemical warmer. In order to introduce air into a chemical warmer, the conventional chemical warmers usually utilize an air-permeable inner bag which is enclosed in an air-impermeable outer bag, or covered by an air-impermeable film or the like. The inner bag may have one or more air-permeable layers which are provided with many air holes or micropores. Initiation of the heating process occurs when the inner bag is exposed to air. Numerous patents have been granted for improvements in such chemical warmers such as the following U.S. patents: U.S. Pat. No. 4,756,299 issued on Jul. 12, 1988 to Car W. Podella, U.S. Pat. No. 4,268,272 issued on May 19, 1981 to Miyako Taura, U.S. Pat. No. 3,976,049 issued on Aug. 24, 1976 to Iwao Yamashita et al, and U.S. Pat. No. 3,301,250 issued on Jan. 31, 1967 to Ernest C. Glasser.
One of the important factors which affects the thermogenic reaction is the amount of air supply per time unit. Due to the structures of the previous chemical warmers, the rate of air supply is adjustable only to a very imprecise degree. As a result, the heat output from the warmer cannot be effectively controlled. In other words, the temperature of the chemical warmer is not controllable. Moreover, in most prior art, the air cannot be efficiently and uniformly supplied to all parts of the thermogenic material, causing hot and cold spots. Furthermore, the thermogenic reaction or heating process is not easily stopped when desired as to the prior art. Normally, the conventional chemical warmer must be taken away from the heated body and put back into an air impermeable bag or resealed by a film in order to stop the production of heat.
Another important factor which affects the uniform heat output throughout the warmer or blanket is the manner of containing the exothermic materials. In conventional warmers, the powdered exothermic material or composition is merely placed loose between two loose covers which form a bag or envelope. This structure has been shown by the U.S. Pat. No. 4,268,272, U.S. Pat. No. 3,976,049, U.S. Pat. No. 4,516,564, U.S. Pat. No. 4,756,299. With this configuration, the powdered exothermic material tends to gravitate all to one place, like a bag of dirt, and cannot be kept in place. Accordingly, the heat cannot be evenly distributed throughout the heated area, especially in the case of a big warmer, such as a blanket.
All of these shortcomings associated with the conventional chemical warmers limit their applications or areas of use.
The present invention provides a novel chemical warmer which overcomes the limitations and shortcomings of the prior art devices.